This invention relates to testing wiring harnesses.
Wiring harnesses are utilized in electrical systems to interconnect various remotely located components and devices of the system. In the automotive field for example, wiring harnesses connect various electrical devices at various locations in a vehicle into operative circuits. Such wiring harnesses are pre-fabricated assemblies which consist of a number of individual wires bundled together and having termination points for connection to the various respective electrical components and devices. A typical wiring harness may for example comprise a number of individual connector plugs at various locations which contain termination points for connection with termination points of mating connector plugs on components and devices. Certain connector plugs may provide for connection with mating connector plugs of other wiring harnesses. In this way wiring harnesses form a network to interconnect the various components and devices into an operative electrical system. A complicated wiring harness may comprise many individual electrical circuits and many individual connectors.
Wiring harnesses are fabricated with the use of manual labor in many instances. As such, the assembly process is susceptible to human error. In order to minimize and hopefully eliminate completely the occurrences of such errors, the use of testing apparatus is desirable to insure that the wiring harness is properly assembled. If an improperly assembled wiring harness is installed in a vehicle, the task of repairing the harness can involve a substantial amount of time and expense because not only can it be difficult to trace the fault, but removal of an installed harness and its subsequent reinstallation are often considerably more difficult than making the electrical repair of the harness.
Therefore, checking of a wiring harness at different stages of its fabrication process is a desirable means to guard against an improperly fabricated harness. Although such testing of harnesses involves an additional operation or operations, and hence is an addition to the piece cost, it can in the long run be cheaper than the substantial costs which will typically be required to repair improperly fabricated harnesses after they have been installed in vehicles. This consideration renders usage of testing equipment desirable and cost-effective. If testing can be performed with greater reliability and speed, this serves to make the testing procedures even more cost-effective. Versatility of testing apparatus makes it still more cost-effective.
The present invention is directed to a new and improved means for testing wiring harnesses which possesses significant advantages over other types of test equipment. It is adaptable to perform testing during and/or after the fabrication of a wiring harness. It is readily adaptable to different harness configurations so that a single test apparatus can be used to check many different types of harnesses. The invention can be embodied in a compact, portable unit. It advantageously makes use of solid-state devices for size, reliability, low power consumption and speed.
One of the aspects which makes the present invention especially advantageous is the test circuit configuration for conductivity testing of the individual circuits of a wiring harness. For the most part conductivity testing involves checking the wiring harness for open circuits and short circuits. The configuration of the present invention is well-adapted to do not only open and short tests, but it also has the ability to test for other effects such as unidirectional conductivity which exists in the presence of unidirectional conductive devices (diodes) in a harness and such as resistance. High-speed operation is achieved by means of a microprocessor-based controller and accompanying electronically operated devices.
The foregoing features, benefits, and advantages of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.